The overall objective is to gain an understanding of how protein-protein and protein-lipid interactions create functionally important structures in biological membranes. To investigate protein-lipid interaction, we shall study by direct means the binding of both lipids and lipid analogs to several purified membrane proteins. As one example of protein-protein interaction, we shall study the self-association of polypeptide chains in the Ca ions -activated ATPase from sarcoplasmic reticulum. The latter protein is an example of an ion pump, in which the metabolic energy of ATP is converted into electrochemical energy to transport an ion against the prevailing concentration gradient. We plan to carry out similar studies using the anion transport protein of the erythrocyte and the visual receptor protein rhodopsin from the retinal rod outer segments.